Pump comprising a water supply

ABSTRACT

A pump ( 12 ) for generating pressure and/or negative pressure comprises a pump chamber having a high-pressure port ( 16 ) and a low-pressure port ( 14 ), and two at least two-blade rotors which are mounted in the pump chamber on two parallel shafts offset in relation to each other. The rotors roll off onto each other free of contact during rotation while forming cells with an internal compression. Provision is made for a supply of a cooling agent ( 21 ) into the pump chamber, the supply being closed-loop controlled depending on the temperature on the side of the high-pressure port ( 16 ).

BACKGROUND OF THE INVENTION

The invention relates to a pump for generating pressure and/or negativepressure, comprising a pump chamber having a high-pressure port and alow-pressure port, and two at least two-blade rotors which are mountedin the pump chamber on two parallel shafts offset in relation to eachother, the rotors rolling off onto each other free of contact duringrotation while forming cells with an internal compression. Pumps of thisdesign are also referred to as claw-type compressors.

In the known claw-type compressors, the heat developing duringcompression is dissipated by means of a cooling air flow at the outersurface of the housing provided with cooling fins or by a cooling watercirculation integrated in the housing.

BRIEF SUMMARY OF THE INVENTION

The invention provides a further development of a pump of the typementioned above to the effect that at least a substantial portion of theheat of compression is eliminated via a cooling agent introduced intothe compressor space. In accordance with the invention, provision ismade for a supply of a cooling agent into the pump chamber, the supplybeing closed-loop controlled depending on the temperature on the side ofthe high-pressure port. The temperature-dependent closed-loop control ofthe volume flow of the cooling agent supplied reliably prevents the pumpfrom overheating under heavy-duty operating conditions. For this reason,the pump according to the invention is suitable in particular for use incombination with fuel cells in motor vehicles. Further essentialadvantages are as follows:

-   -   compact design owing to a reduced requirement of external        cooling;    -   small temperature differences in operation because the heat of        compression is dissipated directly at the place where it        develops;    -   smaller gaps between the rotors and the housing and, hence,        improved efficiency;    -   humidification of the compressed air, as is of advantage in        certain processes.

Water is especially suited to serve as cooling agent.

In the preferred embodiment of the invention, at least one injectionnozzle for the cooling agent is arranged to open into the pump chamber,preferably a two-component atomizer nozzle which, in addition to theliquid cooling agent, is supplied with a gaseous volume flow which isbranched off from the high-pressure port. The two-component atomizernozzle is provided with a flow regulating member which is engaged by anactuating drive.

BRIEF DESCRIPTION OF THE DRAWINGS

Details of the invention will be apparent from the accompanying drawingsin which:

FIG. 1 shows a schematic diagram of the pump in accordance with theinvention, having a temperature-controlled water supply fed directlyinto the compressor space and using an adjustable two-component atomizernozzle;

FIG. 2 shows a diagrammatic sectional view of a claw-type compressorhaving a temperature-controlled water supply according to the schematicdiagram of FIG. 1;

FIG. 3 shows a variant of the claw-type compressor of FIG. 2, in whichthe system pressure on the outlet side is made use of for atomization ofthe cooling water supplied; and

FIG. 4 shows a diagrammatic section of a claw-type compressor having atemperature-controlled water supply fed directly into the compressorspace and using a controllable injection pump.

DETAILED DESCRIPTION OF THE INVENTION

The schematic diagram illustrated in FIG. 1 shows a pump 12 which isoperated by an electric motor M and is connected with a suction pipe 14on the input side and with a pressure pipe 16 on the output side. Agaseous medium having a pressure P₀ and a temperature T₀ may be suppliedto the pump 12 via the suction pipe 14 and a gaseous medium having apressure P₂ and a temperature T₂ may be discharged from the pump via thepressure pipe 16. Opening into the suction pipe 14 there is atwo-component atomizer nozzle 18 which may be supplied with coolingwater 21 via a cooling agent supply 20 and with compressed air via acompressed air supply 22. The two-component atomizer nozzle 18 isprovided with a flow regulating member which may be actuated via anengaging actuator drive 24. The quantity of cooling water to be fed inis determined via a closed loop. For the closed-loop control atemperature sensor is provided in the pressure pipe 16 which measuresthe temperature T₂ of the gaseous medium exiting the pump 12. Thetemperature T₂ as measured is compared with a set point T_(s) and thetemperature difference T₂−T_(s) is deviation-controlled by the flow ofthe liquid cooling agent by means of driving the actuator drive 24.

FIG. 2 shows the pump in accordance with the invention as illustrated inFIG. 1 in a diagrammatic sectional view. The pump 12 includes a housing30 having a pump chamber 32 formed therein. Inside the pump chamber 32,two two-blade rotors 34, 36 are each supported on a shaft 38, 40. Theshafts 38, 40 are arranged to be parallel and offset in relation to eachother. The rotors 34, 36 roll off onto each other free of contact duringrotation while forming cells 42 of variable size, with an internalcompression taking place. The heat arising in operation of thisso-called claw-type compressor 12 is substantially dissipated by thetemperature-controlled water supply as described in FIG. 1. The amountof water required for cooling is atomized via the two-component atomizernozzle 18 directly into the pump chamber 32.

In the pump shown in FIG. 3, for elements which correspond to elementsshown in FIGS. 1 and 2, the same reference numerals are used increasedby “100.” In the pump shown in FIG. 4, for elements which correspond toelements shown in FIGS. 1 and 2, the same reference numerals are usedincreased by “200.”

The claw-type compressor 112 depicted in FIG. 3 corresponds to theclaw-type compressor 12 depicted in FIG. 2. In contrast to the closedcooling loop illustrated in FIG. 2, in this case the gaseous volume flowsupplied to the two-component atomizer nozzle 118 is branched off fromthe pressure pipe 116 and is returned to the two-component atomizernozzle 118 via a conduit 144. The system pressure on the outlet side ismade use of in this way for atomization of the cooling water 121supplied.

In the embodiment illustrated in FIG. 4, the cooling water 221 issupplied into the pump chamber 232 of the claw-type compressor 212directly via a controllable injection pump 250. The quantity of coolingwater to be supplied by the pump is closed-loop controlled using thetemperature T₂ of the gaseous medium exiting the pump chamber 232 in away analogous to the schematic diagram of FIG. 1.

In accordance with a further embodiment according to the invention,provision is made that the liquid cooling agent is not fed directly intothe pump chamber by the controllable injection pump, but is supplied viaan injection nozzle connected between the pump chamber and the injectionpump.

Provision is further made in accordance with the invention that theinjection nozzle opens into the pump chamber in the area of the pressurepipe or that an injection nozzle in addition to the injection nozzle inthe area of the suction pipe opens into the pump chamber in the area ofthe pressure pipe.

The temperature-controlled supply of the cooling water directly into thepump chamber serves to reliably avoid overheating of the pump even underheavy-duty conditions of use. In comparison with pumps having anexternal cooling as known from the prior art, the pump in accordancewith the invention presents the advantage that it requires less space asa result of its compact design. Since the heat generated on compressionis dissipated directly at the place where it develops, namely in thepump chamber, only small temperature differences appear between thehousing and the rotors, as compared with a pump having an externalcooling, resulting in a minimum temperature expansion of the rotorsoccurring in operation so that the pump may be designed with very smallgaps between the rotor and the housing. As a result of the gapreduction, backflows are minimized and the efficiency is optimized.

1. A pump for generating pressure and/or negative pressure, comprising apump chamber having a high-pressure port and a low-pressure port, andtwo at least two-blade rotors which are mounted in said pump chamber ontwo parallel shafts offset in relation to each other, said rotorsrolling off onto each other free of contact during rotation whileforming cells with an internal compression, a supply of a liquid coolingagent is provided to the pump chamber, said supply being closed-loopcontrolled depending on the temperature on the side of the high-pressureport, and at least one two-component atomizer nozzle for said coolingagent arranged to open into said pump chamber wherein, in addition tothe liquid cooling agent, a gaseous volume flow which is branched offfrom the high-pressure port is supplied to the two-component atomizernozzle.
 2. The pump as claimed in claim 1, wherein the cooling agent iswater.
 3. The pump as claimed in claim 1, wherein said at least oneatomizer nozzle opens into the pump chamber in the area of thelow-pressure port.
 4. The pump as claimed in claim 1, wherein said atleast one atomizer nozzle opens into the pump chamber in the area of thehigh-pressure port.
 5. The pump as claimed in claim 1, wherein thetwo-component atomizer nozzle is provided with a flow regulating memberwhich is engaged by an actuating drive.
 6. The pump as claimed in claim1, wherein said atomizer nozzle is fed by a controllable injection pump.7. The pump as claimed in claim 1, wherein the two-component atomizernozzle is provided with a flow regulating member which is engaged by anactuating drive.